A common requirement in an asynchronous transfer mode (“ATM”) switching system is support for termination of a virtual path connection (“VPC” or “F4 connection”) into its associated virtual channel connections (“VCC” or “F5 connection”). Such termination necessitates support for operations, administration and management (“OAM”) alarm notification and cell generation in accordance with the ITU-T I.610 and GR-1248-CORE standards. Specifically, if an F4-AIS (“Alarm Indication Status”) cell is received, that cell is terminated and a VP-AIS alarm is raised. Within 500 milliseconds (“msec”) of the F4 connection receiving the AIS cell (and subsequently declaring the VP-AIS alarm state), all F5 connections associated with that F4 connection must generate a VCC-AIS cell downstream. The F5 connections must then generate VCC-AIS cells at a rate of one per second until the F4 connection exits the VP-AIS alarm condition.
Prior art F5-T0-F4 OAM alarm notification and cell generation techniques have been implemented by means of specialized software. However, a potentially large number of connections may be supported by a single ATM switch. Prior art software based techniques are incapable of maintaining compliance with the standards' stringent time limits for large numbers of connections in terms of alarm notification and OAM cell generation. It is accordingly apparent that OAM support for F4 termination cannot be managed by software but must be managed by special hardware provided at the ATM Layer. This is facilitated by the present invention.